The present invention relates generally to a cover constructed of polymeric material that is substantially cup shaped and which has a bottom having stiffening ribs on its interior.
Such covers are generally known and used, for instance, to cover belt pulleys or as the valve covers of an internal combustion engine. The stiffening ribs are provided in order to minimize warping of the cover caused by manufacture. The warping is caused by varying shrinkage of material in different regions of the cover so that torsion is produced along the longitudinal axis of the cover. Stiffening ribs which are integrally developed have the disadvantage that relatively high forces are required while fastening the cover in order to overcome the slight warping which remains, and to align the sealing surface approximately parallel to the mating surface. Particularly when soft seals of elastomeric material are used, such as are employed, for instance, for the acoustic decoupling of the cover, the danger exists that the cover will be mechanically overstressed and/or damaged upon its mounting.
There remains a need to provide a cover of polymer material (and a method for its manufacture) that is dimensionally stable and torsionally rigid and that has a fastening flange with a flat sealing surface.